Introduction

ffmm is a python implementation of fast Fourier Modal Method (FMM). As periodic photonic structures, such as crystals, are becoming more and more important in many applications, FMM has become a popular tool for solving problems related to these structures. For acedamic purposes, \(S^4\) is a popular choice for the FMM.

\[\nabla^2 u = 0\]

where As show in Eq.